Qubit Zoo

Bifluxon: Fluxon-Parity-Protected Superconducting Qubit

1 min read

Proposes and analyzes the cos(2φ) qubit (bifluxon), a protected superconducting qubit where both charge and flux matrix elements between qubit states are exponentially suppressed. The potential energy is π-periodic in the superconducting phase, creating protected degeneracy.

Key Results

  • Simultaneous protection against charge and flux noise
  • Exponential suppression of both bit-flip and phase-flip matrix elements
  • Requires superinductance + junction pair with controlled asymmetry
  • Predicted T₁ enhancement: 10²–10⁴× over transmon

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